如何在 NS-3 中使用多路径路由

Question

我是NS-3的初学者，我想通过NS-3在我的网络中配置多路径路由，代码如下：

#include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/csma-module.h"
#include "ns3/internet-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/applications-module.h"
#include "ns3/ipv4-global-routing-helper.h"

using namespace ns3;
using namespace std;

NS_LOG_COMPONENT_DEFINE ("TestRoutingExample");

int main(int argc, char *argv[]) 
{
    LogComponentEnable ("UdpEchoClientApplication", LOG_LEVEL_INFO);
    LogComponentEnable ("UdpEchoServerApplication", LOG_LEVEL_INFO);

    Ptr<Node> n0 = CreateObject<Node>();
    Ptr<Node> n1 = CreateObject<Node>();
    Ptr<Node> n2 = CreateObject<Node>();
    Ptr<Node> n3 = CreateObject<Node>();
    Ptr<Node> n4 = CreateObject<Node>();

    Names::Add("n0", n0);
    Names::Add("n1", n1);
    Names::Add("n2", n2);
    Names::Add("n3", n3);
    Names::Add("n4", n4);

    NodeContainer n0n1(n0, n1);
    NodeContainer n1n2(n1, n2);
    NodeContainer n1n3(n1, n3);
    NodeContainer n3n4(n3, n4);
    NodeContainer n2n4(n2, n4);

    NodeContainer global(n0, n1, n2, n3, n4);

    // create link
    PointToPointHelper p2p;
    p2p.SetDeviceAttribute ("DataRate", StringValue ("5Mbps"));
    p2p.SetChannelAttribute ("Delay", StringValue ("2ms"));
    NetDeviceContainer d0d1 = p2p.Install(n0n1);
    NetDeviceContainer d1d2 = p2p.Install(n1n2);
    NetDeviceContainer d1d3 = p2p.Install(n1n3);
    NetDeviceContainer d2d4 = p2p.Install(n2n4);
    NetDeviceContainer d3d4 = p2p.Install(n3n4);
    // create internet stack
    InternetStackHelper internet;
    internet.Install (global);

    Ipv4AddressHelper ipv4;

    ipv4.SetBase ("10.0.0.0", "255.255.255.0");
    Ipv4InterfaceContainer i0i1 = ipv4.Assign (d0d1);

    ipv4.SetBase ("10.1.1.0", "255.255.255.0");
    Ipv4InterfaceContainer i1i2 = ipv4.Assign (d1d2);

    ipv4.SetBase ("10.2.2.0", "255.255.255.0");
    Ipv4InterfaceContainer i1i3 = ipv4.Assign (d1d3);

    ipv4.SetBase ("10.3.3.0", "255.255.255.0");
    Ipv4InterfaceContainer i2i4 = ipv4.Assign (d2d4);

    ipv4.SetBase ("10.4.4.0", "255.255.255.0");
    Ipv4InterfaceContainer i3i4 = ipv4.Assign (d3d4);


    Config::SetDefault("ns3::Ipv4GlobalRouting::RandomEcmpRouting",     BooleanValue(true)); // enable multi-path routing
    Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

    // install application
    UdpEchoServerHelper echoServer1(9999);
    ApplicationContainer serverApps1 = echoServer1.Install (n4);
    serverApps1.Start (Seconds (1.0));
    serverApps1.Stop (Seconds (1000.0));

    // n0 -> n4
    UdpEchoClientHelper echoClient1(i2i4.GetAddress (1), 9999);
    echoClient1.SetAttribute ("MaxPackets", UintegerValue (200));
    echoClient1.SetAttribute ("Interval", TimeValue (Seconds (1)));
    echoClient1.SetAttribute ("PacketSize", UintegerValue (1024));
    ApplicationContainer clientApps1 = echoClient1.Install (n0);
    clientApps1.Start (Seconds (2.0));
    clientApps1.Stop (Seconds (10.0));

    // dump config
    p2p.EnablePcapAll ("test");

    Simulator::Run ();
    Simulator::Destroy ();

    return 0;
}

拓扑如下：

n0会周期性的向n4发送UDP包，但是我查看.pcap文件发现所有的包都是走n0→n1→n2→n4的路径，为什么？

Answer 1

看看dynamic-global-routing.cc example. Basically you can do this by enabling RespondToInterfaceEvents:

Config::SetDefault ("ns3::Ipv4GlobalRouting::RespondToInterfaceEvents", BooleanValue (true));

RespondToInterfaceEvents: Set to true if you want to dynamically recompute the global routes upon Interface notification events (up/down, or add/remove address)

并关闭节点 n1 或 n4 上的接口之一（因为在您的情况下它们都有两个接口）。所以它应该看起来像这样：

Ptr<Ipv4> ipv41 = n1->GetObject<Ipv4> ();
// The first ifIndex is 0 for loopback, then the first p2p is numbered 1,
// then the next p2p is numbered 2
uint32_t ipv4ifIndex1 = 1; // since you first installed d1d2

Simulator::Schedule (Seconds(4), &Ipv4::SetDown, ipv41, ipv4ifIndex1);
Simulator::Schedule (Seconds(6), &Ipv4::SetUp, ipv41, ipv4ifIndex1);

按照这种方法，您可以扩展它并随机触发 SetDown 和 SetUp 事件。希望对您有所帮助。

更新：如果您想使用 RandomEcmpRouting，您必须将 SetDefault 调用移到顶部（在创建接口之前）。

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